1. Field of the Invention
The present invention relates to a camera device, and more particularly to a high sensitivity camera device which is made highly sensitive by extending the storage time of the image pickup element than in the conventional device.
2. Description of the Prior Art
FIG. 3 is an example of a prior art highly sensitivity camera device, which shows an RGB three chip type high sensitivity color camera device that uses charge coupled devices (referred to as CCDs hereinafter) as image pickup elements. In each of the RGB channels, a CCD 1 is a photoelectric conversion element which converts an optical information to an electrical signal. A picture signal processing circuit 2 is a signal processing circuit which performs a specific processing such as gamma correction in order to convert the output of the CCD 1 to a picture signal. A frame memory 12 stores the output of the picture signal processing circuit 2 by means of a control signal, sent from a control circuit 11, which is linked to a charge read timing of a read interval control circuit 8, and converts an intermittently output picture to a picture continuous over the entire field or entire frame by repeatedly outputting the same picture until the next charge read. The read interval control circuit 8 is a circuit which controls the time interval of read pulses for transferring the charge stored in a charge storage part of the CCD 1 to a transfer part.
During the normal image pickup, the signal charge stored in the charge storage part is transferred to the transfer part for every field or every frame. However, during the high sensitivity image pickup, the time interval of the read pulses is set to an integral multiple of the field or frame period using an internally or externally set control signal in order to realize high sensitivity by making an arrangement to store the signal charge for a longer time in the charge storage part. The memory control circuit 11 is a circuit for controlling the read or write of the frame memory 12 linked with the charge read timing. A synchronizing signal generating circuit 9 is a circuit which generates a synchronizing signal necessary for the picture signal processing circuit 2 and a timing signal necessary for the read interval control circuit 8 and the memory control circuit 11.
FIG. 4 is a diagram describing the operation during the high sensitivity image pickup for the constitution as shown in FIG. 3, and shows an example in which the signal charge in the CCD 1 is stored over two frame periods. In the figure, signal A stored in the charge storage part of the CCD 1 for two frame periods is output at the time t.sub.O. The signal A output from the CCD 1 is sent through the picture signal processing circuit 2 and is stored in the frame memory 12. In the frame memory 12, the same picture A is output repeatedly over the two frame periods until the time t.sub.1 at which the next signal B is read.
However, in the high sensitivity camera device according to the prior art, intermittent pictures are converted to a continuous picture in terms of a frame memory, so that the picture is changed only in every several fields or several frames, and there is a drawback in that the motion of an object in the picture is unnatural.